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Why does mph at ¼ mile matter?

Discussion in 'Drag Racing' started by Brian A, Apr 28, 2008.

    • Member

    Brian A

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    Okay, okay, I know almost zip about drag racing, but I am curious about something.

    Why are the results always reported both as time and a speed? As I understand it, it's about traveling a ¼ mile from a standing start in as little time as possible. What does it matter what the final speed was? What does it say about how the car ran?

    Even Wikipedia doesn't explain this.
    • Member

    MGarrison

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    I don't know the history of drag racing, but it's probably been that way since people started drag racing, due to your typical human's/racer's/adrenaline junkie's interest/fascination/obsession with speed.

    It seems a human thing to be interested in speed. Not everyone enjoys going fast, but I would suspect any sensation faster than one could walk or run has been a rush (although maybe a frightening one) ever since some proto-human ancestor accidentally slipped on the rocks and got rushed down the river rapids.

    Cliff-diving, riding on running animals, sliding down a slippery hill, horse teams pulling chariots - seems like people have been interested in how quickly you or someone else can go, or get from point A to B, for ages.

    With cars, it just seems natural to ask how fast can it go? How fast did it go? With the creation of instruments capable of measuring instants of time, it becomes possible to quantify the 'how long did it take to go that fast/far?' question. So, the 1/4 mile measurements give a common reference frame for speed and time.

    So, although it's a guess, I would think it's more tradition than anything else. Let's say you got to 1000mph in 1/8 of a mile but your engine blows and you screech to a near halt, rolling across the finish line two minutes after your opponent. You lose the race, but it's still worthwhile to know what speed you reached - if you could make the engine survive, that tells you what potential you might have to win the race. I don't know much about the specifics of drag racing, but just like in regular racing, I bet the pro teams measure every parameter they possibly can.

    Virtually every single (non-track-junkie) person I ever have a conversation with about BMWCCA driver's schools, they don't ask how many g's I pull in a turn, or what's my lap time, or what was my exit speed out of the keyhole at Mid-Ohio - there's only one question: how fast do you go at those? Which always is replied to with an explanation that it's more about carrying speed/momentum through turns than it is about straightline top speed. However, that's driver's schools, not drag racing. :)
    • Member

    az3579

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    Well think of it this way...


    You are standing a quarter mile away from a starting point. The cars finally approach. You see one's faster than the other at that point.



    That's why it matters. :)


    I generally find that the faster the speed, the faster the time, but I may have overlooked that...

    Dr Obnxs guest

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    It tells you something more about how the car works..

    It's indicative about how well a car puts power to the ground and the shape of the torque curve. While you aren't judged on speed, it does say something about how the car achieved the time...

    Matt

    Musikpro guest

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    I'm gonna state the obvious

    I think they report the speed because people are lazy and don't want to calculate the speed for themselves (velocity=distance/time)... Plus, we like cool toys... and if we have a device that can measure speeds and times to a very fine degree... WHY NOT! :D

    CCContact guest

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    Terminal Speed

    In drag racing speed is measured in the last 60 feet of the quarter mile, so it's the terminal speed at the finish line. It used to measured over 120 ft., 60 ft. and before and 60 ft. after the finish line, but the insurance weenies were concerned about high speeds of the nitro classes and this had the effect of showing speeds a few miles an hour slower. So it's not the average speed, which could be computed, and just as well since the cars can perform so differently depending on the tuneup and conditions.

    The stats are interesting in that they can show exactly how the race went, each lane being timed individually. Car A may have a reaction time of .04 with a 4.66 elapsed time for a total of 4.70 seconds. If he burns a few pistons at the 1100 foot mark, the speed can drop down to the 280's with litte effect on the elapsed time. Car B meanwhile runs a 4.64 but with a .08 reaction time, for a total of 4.72 seconds. So he loses by 2 hundredths of a second, but if he was hitting on all 8 cylinders all the way (not easy!) he may achieve 320 mph in the speed trap. This is not uncommon and makes for some great replays on the TV broadcasts, not to mention at the track.

    Tuning the nitro cars is a real science, with computers limited to data loggers. The crew chiefs all have their secrets and the best are paid well into 6 figures if they can get the car consistently down the track in the top half of the field. So while the speed itself isn't critical, it does give the tuner an idea of how much horsepower he's making, not to mention running cleanly to the finish without one of the spectacular but dangerous "grenades."

    Dennis

    Dr Obnxs guest

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    Me too!

    Maybe it's because poster are lazy and don't think about the difference between average speed and instantaneous speed! ;)

    But maybe not... The poster before has better details.

    Matt

    Musikpro guest

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    thought about... yes... CARED about... not so much! lol... I was just being facetious.

    I'm not into dragging, but as that previous poster noted, there are uses for those seriously into it... and as with anything... there are those who FIND it interesting, and there are those MAKE it interesting. If you are willing to invest the time (and money) into it, you could analyze the crap out of whatever it is you want. (and whether or not that information is any good, well... that depends on who uses it and for what).

    Dr Obnxs guest

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    There was an internet e-mail going around

    about some interesting data from top fuel funny cars.... A couple I remember...

    The blower takes more power to spin that most big block V8s can put out.

    The magnetos push more current than arc welders.

    The white you see in the exhast at night drags is the hydrogen from dissacociated water burning in the air...

    The dump so much fuel in there that the engines are running just a hair shy of hydro-lock.

    A 200 mph car crossing the starting line at top speed would still loose the race...

    While it does have it's fans and those that don't care that much, it's at the cutting edge of power generation in internal combustion engines. And to think, they get 45 min between each race to basically rebuild the motor. That's pretty amazing itself!
    • Member

    az3579

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    They'd give Formula 1 cars a run for their money!

    I saw this program on History channel that had a small segment in those dragsters. I think they average a good 1/4 mile to a gallon and produce north of 8,000 horsepower!!

    I have a hard time believing that a car passing the starting line at 200 mph would lose to the dragster though. I just don't see it happening; 1/4 mile is not a long distance by any means.

    Dr Obnxs guest

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    What's surprising is how close it would be....

    I found a time of 4.567 sec with a top speed of 321 mph. If that's true a 200 mph car would be 17 feet ahead at the quarter mile. I found another time of 4.441 seconds, and then the dragster wins!

    here's the post I quoted some from. Some of the stuff is pretty impressive.

    ********************************************************************************************************

    Some interesting stuff for the horsepower inclined...

    # One Top Fuel dragster's 500-cubic-inch Hemi engine makes more horsepower than the first four rows at the Daytona 500.

    # A stock Dodge Hemi V-8 engine cannot produce enough power to drive the dragster's supercharger.

    # With 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into a near-solid form before ignition. Cylinders run on the verge of hydraulic lock at full throttle.

    # At the stoichiometric 1.7:1 air-fuel mixture for nitro methane, the flame front temperature measures about 7000 degrees Fahrenheit.

    # Nitro methane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, separated from atmospheric water vapor by the searing heat of the exhaust gases.

    # Dual magnetos supply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

    # Spark plug electrodes can be totally consumed during a single pass. After half-distance, the engine is dieseling from compression plus the glow of exhaust valves at 1400 degrees Fahrenheit. The engine is shut down by cutting the fuel flow.

    # If a spark plug fails early in the run, un-burned nitro can build up in the affected cylinder and explode with sufficient force to blow the cylinder head off in pieces or split the cylinder block in half.

    # In order to exceed 300 mph in 4.5 seconds, dragsters must accelerate at an average of more than 4 g's. In order to reach 200 mph before half-distance, the launch acceleration approaches 8 g's. A Top Fuel dragster reaches more than 300 mph before you have completed reading this sentence.

    # With a redline that can be as high as 9500 rpm, Top Fuel engines turn approximately 540 revolutions from light to light. Including the burnout, the engine needs to survive only 900 revolutions under load.

    # Assuming that all of the equipment is paid off, the crew works gratis, and nothing breaks, each run costs an estimated $1000 per second.

    # The current Top Fuel dragster elapsed time record is 4.441 seconds for the quarter-mile (October 5, 2003, Tony Schumacher). The top-speed record is 333.25 mph as measured over the last 66 feet of the quarter-mile (November 9, 2003, Doug Kalitta).

    # Putting all of this into perspective: You are driving the average $140,000 Lingenfelter twin-turbo Corvette Z06. More than a mile up the road, a Top Fuel dragster is staged and ready to launch down a measured quarter-mile as you pass. You have the advantage of a flying start. You run the Vette up through the gears and blast across the starting line and past the dragster at an honest 200 mph. The "tree" goes green for both of you at that moment. The dragster launches and starts after you. You keep your foot down, but you hear a brutal whine that sears your eardrums, and within three seconds, the dragster catches you and beats you to the finish line, a quarter-mile from where you just passed him. From a standing start, the dragster spotted you 200 mph and not only caught you but nearly blasted you off the road when he passed you within a mere 1320 feet.

    **************************************************************************

    Matt
    • Member

    Brian A

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    What about "normal" cars?

    On page 148 and 149 of the May 2008 "Road & Track" magazine, there are a bunch of 1¼ mile statistics for a bunch of cars. Picking the pack surrounding the 335i, I find this:

    13.4 sec @ 100.0 mph - Lotus Exige S
    13.4 sec @ 105.3 mph - Porsche Cayman S
    13.5 sec @ 103.1 mph - Lexus IS 350
    13.5 sec @ 103.5 mph - BMW Z4 M Coupe
    13.5 sec @ 104.5 mph - BMW 335i
    13.5 sec @ 105.0 mph - BMW 550i
    13.6 sec @ 98.2 mph - Subaru Impreza WRX STi
    13.6 sec @ 100.9 mph - Mitsubishi Lancer Evolution GSR
    13.7 sec @ 104.4 mph - Aston Martin V8 Vantage

    It doesn't make sense (nor does it make sense why I am becoming obsessed about figuring this out). Any ideas?

    EDIT:
    Here is some extra information on these cars. The horsepower, torque and weight are all over the place. No obvious corelations. Maybe its related to gearing or tires or something:

    220 hp, 165 ft lbs, 2030 lbs - Lotus Exige S
    295 hp, 251 ft lbs, 3150 lbs - Porsche Cayman S
    306 hp, 277 ft lbs, 3615 lbs - Lexus IS 350
    330 hp, 262 ft lbs, 3295 lbs - BMW Z4 M Coupe
    300 hp, 300 ft lbs, 3635 lbs - BMW 335i
    360 hp, 360 ft lbs, 3945 lbs - BMW 550i
    305 hp, 290 ft lbs, 3360 lbs - Subaru Impreza WRX STi
    291 hp, 300 ft lbs, 3555 lbs - Mitsubishi Lancer Evolution GSR
    380 hp, 302 ft lbs, 3605 lbs - Aston Martin V8 Vantage

    Paleoc guest

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    The final speed can tell you a lot about how well the car launches. For example, if you finish with a high speed for the time you ran, it can indicate that your car launched poorly, perhaps you had excessive wheel spin. It is indicating that your car should run a quicker time with a better launch or better traction. It could also indicate a change of gearing is needed.
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    rdspear

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    The WRX and Evo are all wheel drive, so they get off the line much more quickly than the 335. They don't have the same power so they can't build speed as quickly, so the 335 makes up the lost ground at the start and passes them just before the quarter mile, going several mph faster. The Lotus has great power to weight, accelerating more quickly than the others. But when the speeds get up there, and aero drag becomes important, is doesn't have the pure power and can't accelerate 80-100 as quickly. So, again, the 335 is slower early in the run and fast later in the run. In this case, it hasn't quite caught the Lotus yet, but is travelling 4mph faster at the quarter mile mark and will soon blow on by. The others are all within 1mph or so, which is easily accounted for by traction, launch, gear ratios, etc.

    That's my take.

    301497 guest

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    ET is the elapsed time to cover the quarter mile and determines who wins the drag race. MPH is an important indicator of the horsepower the dragster is generating. Example: Let's say a car runs the quarter in 11.00 @ 131 mph and his competitor runs the quarter in 10.96 @ 129mph. Car #2 wins which could be a result of a better traction or suspension set up in which his car was more efficient at putting the power to the ground or a quicker reaction time.....however, Car #1 generated a higher mph and was producing a little more horsepower....he would then look at areas such as improving reaction time, his drag slicks, the weight transfer of the car at launch, his 60 ft times, etc....to determine how much more efficiently he can harness the horsepower that would result in a lower ET. Make sense? Obviously, this doesn't cover all aspects but I believe it hits on the major ones.
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    182861

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    If a car's limited at 200mph, and since the speed is constant through-out, it would take 4.5 seconds to traverse 1/4 mile (d = vT, distance traveled = velocity x time, so time to cover 1/4 mile at 200 mph. Tony Schumacher set a 1/4 mile time in a Top Fuel dragster of 4.441 seconds on 10/04/03. So it is entirely possible that a car with a top speed of 200 mph would hit the starting line at 200mph, and still lose in the 1/4 mile race to a Top Fuel dragster.

    ForcedInduction guest

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    ET tells how long it takes to cover the 1/4 mile. Speed is an indicator of engine HP. The car with the most HP does not always have the fastest ET or win as there are many factors involved in drag racing or performance testing in the 1/4 mile drags. You will often see Turbo cars with big mph but not a matching low ET.
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    Satch SoSoCalifortified

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    ET versus top speed

    Why do we bother with the speed? Because we're GUYS: And guys grow up with simplistic notions. . . like, "Jeez, how fast will it go?!"

    That's one step removed from, "Mine's faster'n yours." Faster, of course, is usually translated as getting from A to B in a shorter elapsed time.

    Oh. My. God: We've just defined rallying!

    A drag race may be defined as a rally with just one very short, very boring stage.
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    Satch SoSoCalifortified

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    Do the math

    Somebody, he say:



    Haven't been doing a lot of TSD rallies lately, have we?

    At 200 miles an hour, it takes 0.3 minutes to go a mile. That's 18 seconds. So one-fourth of that is 4.5 seconds. All I need is a double-A fuelie---do they still make those?---to beat that by at least half a second.

    It gets better: If you hit the starting line at a steady 90, it'll take you 10 seconds---so I can beat you with any number of modified drag cars.

    Hell, if you hit the line at 60, I'll whip you with a stock M roadster!
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    eam3

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    I was told there'd be no math... :D

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